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The Potter Valley Project


The Potter Valley Project is an interbasin transfer between the Eel River and Russian River watersheds. Included in the operation are two Eel River dams (Scott Dam and Cape Horn Dam), as well as a powerhouse and water diversion facilities.

The name “Potter Valley Project” has long been used to describe the hydropower generation facilities because this is where they are physically located. However, a more accurate name might be the Northern California Water Project since the water supplied by the Potter Valley Project is used by more than 650,000 people downstream of Potter Valley for beneficial uses in Mendocino, Sonoma and Marin Counties.


Who This Affects

In addition to providing power through the powerhouse, the Potter Valley Project also provides water for a variety of beneficial uses including:

  • Community (domestic and industrial water supply)
  • Wildlife & Fish Habitat
  • Agriculture
  • Tribal
  • Recreation
  • Fire Suppression



Mendocino, Sonoma, and Marin counties all benefit from this water. According to Sonoma Water, more than 650,000 people in these three counties depend on water from the Potter Valley Project’s Eel River diversion for their domestic, agricultural, recreational and fire suppression water supplies.

Under the current operation, the Potter Valley Powerhouse has the power-generating capacity to support about 2,000 homes, if a typical home uses 30 kWh/day. The powerhouse has the maximum capacity to generate 9.2 megawatts and three smaller, privately owned powerhouses downstream have the capacity to generate 1.18 megawatts. The diverted water from the Potter Valley Project stored in Lake Mendocino is used again by the City of Ukiah to generate hydropower at their facility with a capacity of 3.5 megawatts.

For fish and wildlife, the water diverted into the East Branch of the Russian River below Coyote Valley Dam helps assure there is enough water to meet the requirements of the Endangered Species Act Biological Opinion. These include in-stream flow requirements of the environmental and recreational use established by the California State Water Resources Control Board, as well as deliveries to cities and water districts in Sonoma and Marin Counties.

All along these 110 miles of river, people live, work, farm, fish, hunt, and recreate. Their dependence on the river is profound. Nearly every aspect of their everyday lives depends on Russian River water. Above the diversion, people in Lake County see economic benefit as well.

Homeowners and visitors who live, fish, hunt and/or recreate in and around the Lake Pillsbury basin contribute significant property and sales taxes.


Current Benefits

Consistent Year-Round Water

Without year-round water, downstream communities would face grave economic impacts.

Communities directly impacted:

  • Potter Valley
  • Redwood Valley
  • Calpella
  • Ukiah Valley
  • Talmage
  • Hopland
  • Cloverdale
  • Geyserville
  • Healdsburg
Clean Water for 31,000 People

Lake Mendocino contributes to drinking water supplies for more than 31,000 people in Redwood Valley, Calpella, Talmage, the Ukiah Valley, Hopland, Potter Valley, and more.

Farm Economics

Farmers from Redwood Valley through Hopland who use water from Lake Mendocino annually generate or support:

  • More than $743 million of the county’s $3.5 billion in revenue
  • More than 5,000 of the 32,000 jobs
  • Approximately $16.1 million in local tax revenue
Essential for Fish Migration

Some of the water stored in Lake Mendocino is dedicated to fishery migration flows that are required at specific times of the year in the Russian River below Lake Mendocino.

Power for 2,000+ Homes

Currently, the Potter Valley Powerhouse has the maximum capacity to generate 9.2 megawatts. Under the current operation, the powerhouse has the power-generating capacity to support about 2,000 homes, if a typical home uses 30 kWh/day.

Wildlife & Ecology

Lake Pillsbury and Lake Mendocino support elk herds, many bird species, mammals such as bears and mountain lions, amphibians, reptiles, and so much more.

Recreational Interests

Winter rainfall and snow melt stored in Lake Pillsbury provide water for summer and fall recreation in Lake Pillsbury, parts of the Eel River, Lake Mendocino, and the Russian River from Coyote Valley Dam to Jenner.

Activities include camping, hiking, biking, fishing, boating, water-skiing, kayaking, canoeing, rafting, swimming, picnicking, and more.

Fire Suppression

Stored water and ag land have helped mitigate the effects of recent wildfires.

  • Lake Pillsbury and Lake Mendocino
  • Agricultural ponds
  • Irrigated fields serve as fire breaks
Helps Feed Ground Water

The water collected from the dams year-round help feed ground water for local communities, such as the city of Ukiah.

What We Stand to Lose and Where We Go From Here

Changes Are Coming

PG&E backed out of relicensing the Potter Valley Project because the Project wasn’t financially viable. Because of this, the water supply provided by the Project will need to be monetized by any entity that continues to run the project water diversion.

Maintain Water Supply Reliability

Water supply reliability is one of the top priorities of IWPC.

Massive Economic Impact

Without year-round water, downstream communities would face grave economic impacts.

Loss of Control

Stored water allows us to have a measure of control in both droughts and floods. Without sufficient water storage, we lose control of our water supply.